What is a Pulmonary Embolism? Where does an embolus (blood clot) come from and what causes an embolus?

A pulmonary embolism occurs when a blood clot lodges in the blood vessels of the lung (pulmonary arteries). The clot is called an embolus, and it most often begins as a clot in the veins of the legs. This is called Deep Venous Thrombosis. This may occur after surgery, particularly after hip surgery or pelvic surgery (such as hysterectomy in a woman or prostatectomy in a man), or after a prolonged period of immobility such as a very long airplane or automobile trip. Some people have a predisposition or tendency toward forming blood clots due to an abnormality in their blood clotting system such as Factor V mutation or Protein C or S deficiency, or Lupus Anticoagulant. Most people, however, have no demonstrable blood abnormality.

Do all pulmonary emboli cause chronic disease?

Pulmonary embolic disease may be acute (occurred within 2 weeks) or chronic (longstanding, having occurred over many weeks, months or years). No, most (acute) pulmonary emboli do not cause chronic disease. In the majority of people the body's own mechanisms will break down those blood clots and in a few weeks to months there will be no trace left of them. Therefore, in most cases, an acute embolus is treated only with anticoagulants such as intravenous heparin or oral Coumadin. There is some debate currently over the most appropriate duration (time) of treatment with Coumadin for acute pulmonary emboli, but most physicians treat for 3 to 6 months. If there are no further episodes, no further treatment is usually given.

In some patients, however, pulmonary emboli recur. If they continue to occur even on Coumadin therapy, a filter is often placed in the main vein leading from the legs to the heart, the Inferior Vena Cava. Such filters are intended to "catch" those clots before they get to the lungs. In most cases this is successful.

Among those people with recurrent pulmonary embolism, some will not completely dissolve the clot then travels to the lungs. Instead the clot itself becomes "organised", meaning that it turns into fibrous tissue. Once this has occurred, the only way to remove it is surgically.

How would I know if I had chronic disease?

Chronic pulmonary thromboembolic disease blocks the flow of blood through the lungs from the right side of the heart to the left. It therefore causes the pressures in the pulmonary arteries to rise. Normally the blood pressure in the lungs is only a fraction of the blood pressure in the rest of your body - the pressure that your doctor measures with a blood pressure cuff. However, with chronic thromboembolic disease the pressures in the lungs may approach those in the rest of the body, or even be higher. This may cause shortness of breath, particularly with exertion, or fatigue. Since these are not very specific symptoms, the condition may be difficult to diagnose. As the condition grows worse, individuals may experience dizziness or syncope (light-headedness leading to loss of consciousness). As the right side of the heart is forced to work harder and harder to pump the blood through the lungs to the left heart, patients may experience chest pain or angina. As the right heart fails to be able to meet the pressure demands, patients may notice swelling of the feet or abdomen.

The diagnosis of chronic pulmonary thromboembolic disease is often made after elevated pressures in the lungs have been discovered - possibly on an Echocardiogram (sound wave picture of the heart). Alternatively, complaints of shortness of breath may have lead to a special scan to look at the blood flow to the lungs, a Ventilation/Perfusion nuclear scan, or a CT ("Computerised Tomography) scan. In either case, the final diagnosis is normally made with a pulmonary angiogram - a dye study of the arteries to the lungs.

Is surgery always possible? When is surgery needed?

Not all patients with chronic thromboembolic disease need surgery, and not all are candidates. Some patients have relatively mild elevations in their pulmonary artery pressures or are not particularly limited by their symptoms. In such cases, pulmonary thromboendarterectomy with its attendant risks (see below) may not be indicated. For example, a young mother of 4 or father holding down two jobs may be limited by disease that, in a 75-year-old sedentary man or woman would not notice.

In addition, in order to perform the procedure, the surgeon needs to be able to reach the fibrous material. In some cases the disease is to far distal - too far out in the small vessels of the lung and not close enough to the main pulmonary arteries - to reach. This can only be assessed by the surgeon and their team, most often on the basis of the pulmonary angiogram.

What are the risks of surgery?

The major risks of surgery are the inability to satisfactorily relieve the pulmonary obstruction (inability to remove enough of the scar tissue), and edema or swelling of he lung tissue after the procedure due to the large amount of new blood flow. Both may be difficult to predict, and both are probably increased in patients with particularly severe disease - just those who have the most to gain from the procedure. The risk of not surviving the surgery will depend on each individual patient's condition and the nature of their disease, however, in most series, the risk of death is between 5 and 10%.

The risk of surgery depends in part on the experience of the surgeon, the anesthesiologists, and the team of critical care physicians involved. The procedure is being performed with increasing frequency at centers throughout the United States and the world.

How is the surgery done?

The operation is done using the heart-lung machine like other "open heart" operations. It is done through a sternotomy incision, as are most cardiac surgical procedures. With the heart-lung machine the patient's body temperature is lowered sufficiently to permit the pump to be stopped, effectively putting the patient in "suspended animation" while the fibrous tissue or clots are removed from the pulmonary arteries. Once the material has removed, the patient's body is rewarmed back to normal using the heart-lung machine. The procedure may take 6 hours or more to perform. Often the patient is kept asleep for several days after the surgery while the lungs accommodate to the new blood flow.

What would my life be like after surgery?

After surgery the majority of patients experience excellent relief of their symptoms. In most cases the pressures in the lungs are reduced to normal or near normal levels. The right side of the heart then recovers, usually with improvement in the leg swelling which may have been present preoperatively. With time patients can usually be completely weaned off of oxygen therapy, although this often takes a few weeks from surgery to permit the lungs to adjust to their new blood flow. Patient's exercise tolerance usually improves, and we have seen patients go back to playing pick-up basketball games that they had thought were lost to memories! Patients continue to require Coumadin therapy for life to minimise the risk of recurrent disease.